Patent Application
20100111559
This invention relates in general to improvements in a cleaning apparatus of the type used, for example, in electrographic document printers or copiers to remove residual toner, carrier, dust, lint, paper fibers, and the like, from a moving surface, typically in the form of an endless web. More particularly, it relates to a removable web cleaning apparatus having one or more blades that can be precisely and repeatedly positioned adjacent to a moving web that is to be continuously cleaned by the apparatus using a shoe that comprises a “T-shaped” extrusion wherein the extrusion has a rigidity to reduce shoe deformations.
Many electrographic printers/copiers use endless webs for recording and/or transferring images, as well as for conveying image-receiving sheets (typically sheets of paper) between image-transfer and other image-processing stations within the instrument. To assure high quality results, it is necessary to maintain the surfaces of such webs free of particulate contaminates (toner, dust, lint, paper fibers, etc) that may ultimately transfer to the image-receiver sheet or otherwise degrade the quality of images produced thereon. Heretofore, a variety of web-cleaning devices have been devised and used to satisfy this need. One such device is generally referred to as a “blade cleaner” and, as its name suggests, it comprises one or more elongated flexible blades having an edge positioned to contact a moving web to either scrape or wipe particles from the web, depending on the angle of contact between the blade and the web surface. Different types of blade cleaners, both scrapers and wipers, are disclosed, for example, in U.S. Pat. No. 5,426,485 in which cleaning blades serve to remove particulate material from an endless elastic belt used to convey copy sheets in an electrostatic copier.
In U.S. Pat. No. 4,866,483, a blade-type cleaning station is disclosed for use in a tabletop electrostatic printer. Here a pair of spaced, parallel cleaning blades set to operate in a wiping mode, serves to remove or scavenge residual toner from an endless photoconductive image-recording belt following transfer of a toner image to a copy sheet. As the image-recording belt moves along its endless path, scavenged toner falls into a sump from which it is continuously removed by a rotatably driven auger. The rotating auger, which is located in the bottom of the sump, serves to transport the scavenged toner to a remote receptacle that can be readily removed from the machine and emptied by the operator. In this disclosure, the cleaning station is rigidly mounted on the printer's base frame. To gain access to the cleaning station for servicing, and the like, the entire print engine, including the image-recording belt, is mounted on a pivoting frame for movement towards and away from the cleaning station. As it moves towards the cleaning station, the print engine's image-recording belt pressingly engages the respective edges of the cleaning blades and is cleaned by the blades as the belt advances along its endless path. Upon being moved away from the cleaning station, sufficient space is eventually provided to enable the machine operator or service personnel to service the cleaning station, e.g., to vacuum scavenged toner from that portion of the sump directly beneath the cleaning blades, or to replace the cleaning blades themselves.
While the cleaning station disclosed in the above-noted patent affords certain advantages not found in prior devices, it may still be viewed as problematic in certain respects. For example, the rotating auger system used to transport scavenged particles from the blade cleaner to a remote receptacle for removal is a relatively complex and costly component of the machine, one that is subject to eventually fail. Further, since the cleaning station is fixed within the machine frame, pivoting the relatively heavy print engine through a large arc away from the cleaning station can only be accomplished by service access. This, of course, necessitates a relatively formidable and complex mounting mechanism, one that is capable of handling and counter-balancing the relatively heavy weight of the print engine. Ideally, the print engine should remain stationary, and the cleaning station, like most other image-processing stations, should be movable relative to it.
Further, once the print engine has been pivoted to its service position to gain access to the scavenged particle sump for vacuuming, blade replacement, etc., the entire sump is exposed to ambient air, and any air currents in the vicinity of the open sump, as occurs during movement of the print engine, can have the effect of blowing toner, dust, etc. throughout the instrument. Ideally, the scavenged particle sump should be easily removed from the vicinity of the machine frame while scavenged particles are confined therein. Once removed, the sump can then be discarded and replaced with a new sump, or it may be cleaned at a location safely spaced from the machine and then replaced.
In the embodiment disclosed, an endless web to be cleaned is part of a conveyor system used to transport image-receiver sheets past one or more image-transfer stations in an electrophotographic printer. The web-cleaning apparatus comprises a single metallic blade or a pair of cleaning blades, one or both of which are made of a metallic material, positioned to operate in a wiping mode to scavenge particles from the web surface, and a sump housing that serves both to support the cleaning blades and to collect and retain particles wiped from the web by the blades. Preferably, the blades are designed to cooperate with a hard backup “shoe” located on the opposite side of the web surface from that contacted by the blades to produce a uniform wiping pressure across the web width while minimizing any tendency for the web to stretch. It is also preferred that the cleaning apparatus be fabricated so as to be easily removable for cleaning after the sump housing has become filled with particles and have blades that can remove hard to remove toner particles, such as those from chemically prepared toner or that can remove toner from webs that have overcoats to absorb oil from 2-sided prints and to prevent oil contamination to other critical parts of the print engine. Another function of at least one of these blades is to remove paper contamination that sticks to the web and are much harder to remove the toner particles. The blades need to be readily replaced, as needed, with new blades. This replaceability of the blades necessitates a reliable mechanism by which each new blade can be precisely positioned in contact with the web surface exerting a predetermined and uniform pressure on the web across its entire width.
A new blade cleaner apparatus for cleaning particulate material from a moving web in an electrographic printer/copier, including a sump having a sump body with molded components, defining a cavity with integral molded baffles, releasable wiper blades made so that the blades do not fall out when inverted; one, two or more releasable wiper blade(s), each having a distinguishment such that the distinguishment distinguishes one wiper blade from the other wiper blade (one such a distinguishment may be the blade material such as a metallic blade and a polyurethane blade and the metallic blade may be profiled); and a removable cover assembly to facilitate the removal of debris material from the sump without removing the wiper blades. The molded components include stops, placement devices and other components that can engagedly cooperate with springs and other biasing devices. The web-cleaning device is attached to a lower bracket and a backup shoe assembly for selectively positioning the web-cleaning device in a web-cleaning position so that the web-cleaning apparatus pressingly engages said surface.
The invention and its objects and advantages will become apparent upon reading the following detailed description and upon reference to the drawings, in which:
While the present invention will be hereinafter described in connection with a preferred embodiment thereof; it will be understood that it is not intended to limit the invention to that embodiment. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention, as defined by the appended claims.
Referring now to
The above-noted toner images and toned process control patches are then transferred to an intermediate image-transfer member 112 at a transfer nip 114. A cleaning brush 115 prior to recycling the image-recording member through the image-forming process removes any residual toner on the image-recording member 104. The image-transfer member may comprise, for example, an electrically conductive drum 116 having a compliant blanket 118 with a relatively hard overcoat 120. The conductive drum is electrically biased by a power supply 122. The toner images transferred onto intermediate image-transfer member are then re-transferred to an image-receiver sheet S at a transfer nip 124 formed by a relatively small transfer roller 126 and an endless sheet-transport web 128 made of a dielectric material such as a polymer compound. A cleaning brush 130 removes residual toner on member 112.
The image-receiver sheets S are presented to the endless sheet-transport web 128, also referred to as a surface in an electrographic printer and that might have an overcoat to absorb oil from 2-sided prints, at a feed station 132. Web 128 is trained around a pair of rollers 134 and 136, and a motor M serves to drive roller 134 in the direction indicated by the arrow. Motor M also serves to rotatably drive the image recording and image-transfer drums. The image-receiver sheets (e.g., paper or plastic) attach to web 128, at a corona charging station 138, which operates to charge the top surface of the sheet so that it becomes electrostatically attracted to the web. The grounded rollers 134 and 136 serve to charge to the rear side of the web. Toner images are electrostatically attracted, and thereby transferred, to the image-receiver sheets by a suitable electrical bias applied to transfer roller 126 by power supply 140. There are various chargers including a corona charger 138 at the sheet-feed station 132, a detack charger 142 that serves to detack the image-receiver sheets as they wrap around transport roll 136, thereby freeing the sheets for further transport to a toner fusing station, (not shown) as well as a web conditioning charger 144, that serves to discharge the web and neutralize toner images on the web surface for easier cleaning operation. Note, being outside the image frame areas on the image-recording drum, any toned process-control patches transferred to the image-transfer member 112 will re-transfer directly to the transport web in the region between successive image-receiver sheets. These toned patches must be removed from the web before receiving a new image-transfer sheet. Otherwise, the toner from these patches will transfer to the rear side of the image-receiver sheets.
Now in accordance with the present invention, a web-cleaning apparatus 150 is provided for removing not only the random toner particles, dust, paper debris, etc., that may accumulate on the outer surface sheet of the transport web 128 during repeated use of the printing machine described above, but also any relatively heavy deposits of toner that may be transferred to the web as the result of forming the aforementioned process-control patches on the image-recording drum, paper jams, misregistration of the toner image with the image-receiver sheets, etc.
Referring to
Referring to
The lower bracket assembly 154 has a rectangular opening 182 for housing the web-cleaning cartridge; sides with plungers 168 for mating with slot features 166 in the cleaning cartridge 156 and for locking the cartridge in place; front and rear flat surfaces 184, 186 for supporting the web-cleaning cartridge 156 through the end springs 188, one at front and the other at rear of the cartridge, and bearing the end spring load when the cartridge is in its operative condition; a front tab feature 176 that holds the latch bracket 190, the latch 162 and the guide adaptor 177 that has a slanted feature 177a for mating with the front bracket tab slanted feature 174a, and the notched and conically shaped pins 158 described above. The guide adaptor 177 and the latch bracket 190 are held together through 2 bolts. The latch 162 is attached to the latch bracket 190 through 2 bolts.
The web-cleaning cartridge 156 has two end springs 188, one at front and one at rear, that load the cartridge against the shoe until four strategically positioned stops 192 contact the shoe 170. Each end spring 188 is positioned preferably proximate a lip L on one of the sides of the sump. This side could be on the shorter sides, on the front or the back areas of the sump. In one preferred embodiment the end spring(s) are positioned between the sump and the flat surfaces 184, 186 of the lower bracket assembly 154 such that end spring 188 biases the sump towards the shoe 170 until one or more stop(s) 192, shown in this embodiment molded onto the sump, abut against the shoe 170 as shown in
In another embodiment of the web cleaning cartridge 156, the cleaner sump 198 has molded grooves 230A with screw inserts 230D that can be used with proper tool blades (not shown) in a setup fixture (not shown here) to set up each sump so as to fix blade engagement and to eliminate imprecision in the locating features of the molded sump that locate the cleaning blades. Once the screws are set, they can be permanently glued in place as to not move during the operating life of the sump and to prevent any tampering with the set up. A tool blade is a hard metal piece that simulates a perfect geometric configuration of a cleaning blade. If the molded sump is well controlled during its fabrication, the above adjustable feature and set up can be eliminated along with any variability in setting up by the adjuster. Such type of screw inserts have been shown but not described in U.S. Pat. Nos. 6,901,227 and 7,031,634 by F. Ziegelmuller, et al.
Another embodiment, as shown in
For the embodiments discussed below, it is important to have the cartridge 154 seated and locked in the lower bracket assembly 154 and to install these two components as a unit to avoid damaging the end springs 188. These springs could otherwise be damaged if the cartridge was forced into the lower bracket as the spring at rear might interfere with the flat surface 186 of the lower bracket. The web-cleaning cartridge 156 is inserted into the opening 182 of the lower bracket assembly 154 and plungers 168 on the sides of this bracket are pulled out to retract their stems ST and the lower bracket assembly and the web-cleaning cartridge are squeezed until the stems ST mate with the slots 166 on the sides of the sump 198.
The lower bracket assembly 154 with the web-cleaning cartridge 156 lockedly in place is installed into the shoe assembly 152 by inserting the notched and conically shaped pins 158 into mating the hole and slot feature 160 of the shoe assembly rear bracket, as shown in
The web-cleaning cartridge 156 is shown in
The wiper blades 194A and 194B are held into the molded grooves 230A by locking springs 230B and the locking spring is designed to have a thickness with a range from 0.012 to 0.018, preferably 0.015 in. on the held edge, in this embodiment to facilitate the blades installation, removal and alignment with the cover. This creates a tight alignment that also reduces noise generated by the stiffer blade during cleaning.
The web-cleaning cartridge 156 receives and store particles wiped or scavenged from the outer surface of web 128 by the blades 194A and 194B and serves not only to prevent scavenged particles from escaping through the top of the cartridge, but also acts to clean the edges of the web 128 as it passes by, and to store particles deflected from the web 128. The cartridge has a sump housing 198 with several molded features such as the slots 166, the stops 192, a cavity 200 for collecting toner from the web, integral molded baffles 202, a side L for attaching the end springs 188 by pushing the hook against the downstream side of L, slots 210A for receiving tab features 210B in the cover assembly to work as a hinge 210, an upper boss 214 to align the cover assembly notch feature 216 to the sump so fasteners 218 in the cover assembly can be attached to the threaded inserts 220 molded into the sump, best shown in
An explosion view of the web-cleaning cartridge components is shown in
The molded sump housing 198 and components described above in one preferred embodiment are made from an injection-molded plastic having a carbon doping for static dissipative purposes to avoid excessive charge build up.
Preferably, the volume resistivity of such plastic material is between 108 to 1011 ohm-cm.
In the preferred embodiment these seals 222 serve both to minimize any leakage of scavenged particles out of the sides of the sump during use of the cartridge, and have an adhesive on the side facing the lid member and a wear-resistant fabric, e.g., Nylon, on the side facing the web 128. These seals minimize any leakage of scavenged particles from the sides of the sump during use of the cleaning apparatus. The foam portion of the seal needs to be of high resiliency, low density, and a low compression set to maintain a good seal and to reduce any drag torque on the transport web 128. A preferred foam material is R200/U polyester having a density of 2 lb. per cubic cm. The Tricot fabric also serves to reduce friction between the web surface and the seals, and can provide some cleaning of the web surface not covered by the blades.
In another preferred embodiment, these seals 222 are made of plush material such as Acrylic fibers with a backing fabric and an adhesive layer that will face the lip surface at the ends and the plush is designed to be wrapped around the sides of the opening O. The plush seal design provides another level of robustness to damage due to web cross-track motion during web tracking corrections. The foam seal design can be tom by the edges of the web while the plush design is more robust to this type of damage. The plush seals can also reduce the load against the web.
One molded sump component shown in
The cleaning or wiper blades 194A,B (shown in
Since the cover assembly 196 releasably attaches to the top of the sump housing 198 there is the need for additional features such as one or more seals to prevent scavenged particles from escaping through the top of the sump housing, and also enable easy attachment of the cleaning blades and the cover. A gasket seal 234 is permanently attached to the perimeter of the sump seat 232 at the cover assembly-sump interface to prevent scavenged particles from escaping through the top of the sump housing. The gasket seal 234 might have some adhesive on the surface facing the sump to permanently attach itself to the sump. The gasket seal 234 could be made with plush material or foam material. The gasket seal material should have high resiliency, low density and low compression set to maintain good sealing between the sump and cover. A preferred foam material is R200/U polyester having a density of 2 lb. per cubic cm and it might have antistatic additives but other materials having similar properties might e suitable including plushes made of Acrylic, Polyester, or Nylon fibers. The cover also includes a pair of side seals, also sometimes referred to as end dust seals, 222 attached to cover and cooperating with the blades at both ends of the sump housing where the blades ends are placed in the sump. These side seals 222 serve both to minimize any leakage of scavenged particles out of the sides of the sump during use of the cleaning apparatus and to wipe particles from the sides of the web.
In a preferred embodiment these side seals 222 are made of a material that most efficiently prevents the release of dust and other contaminants from the sump housing 198. In a preferred embodiment this includes one of foam, pile, plush material, having high resiliency, low compression set and low density. In one embodiment, the side seals are made of R200/U polyester foam having a density of 2 lb. per cubic cm and having a Tricot fabric attached to the surface facing the web 128 to reduce friction and the load between the web and the seals. The Tricot fabric can provide some cleaning of the web surface not covered by the blades. In another embodiment, the side seals 222 are made of plush material such as Acrylic, Polyester, Polypropylene or Nylon and these fibers could have antistatic additives to reduce charge build up. These side seals 222 may be permanently attached to the cover assembly by having an adhesive on the surface facing the cover. It is important that these side seals have minimum gaps with the ends of the wiper blades. Preferably the gaps between the side seals and the ends of wiper blades should be less than 0.5 mm since ideally you do not want to have a gap but you cannot load the side of the blade without a gap so the gap is minimized.
Also shown in
The sump housing shown in FIGS. 5 and 7C-7D includes several additional features that enable easy attachment of the wiper blades 194A,B. The molded baffles 202 in a preferred embodiment have a plurality of spaced walls that are arranged at a common angle (between about 15 and 45 degrees) relative to the side walls of the sump housing and include one or more notches 236 that prevent misplacement of the wiper blades. Baffle notches 236 are cut to model the wiper blade's asymmetric cross-section so that the operator cannot install the wiper blade incorrectly. If the wiper blade is inverted or sideways the bend in the blade stiffener will interfere with the baffle preventing the operator from installing the blade. This allows the operator to confidently replace the blades and prevent misalignments that could damage the web or reduce blade engagement with the web. The sump housing 198 also has one or more grooves 230A cut in the sump perimeter adjacent the cavity of a shape similar to the wiper blade end-piece 228a,b so that groove 230A and wiper blade end-piece 228a,b can cooperate to assure a precise fit and desired orientation of the wiper blades in the sump. In a preferred embodiment the quick release receiver can be a spring 230B that fits in the groove 230A and a cutout 230C so that the locking spring cooperates with the groove and cutout to clamp against them and hold the blade in place in such a way that the spring is biased to assure a precise fit and desired orientation of the wiper blades in the sump. This spring has also an upper lip formed to prevent incorrect installation of the blades. This allows the consumer to confidently replace the blades and prevents misalignments that could damage the web or result in poor cleaning. The double protection of the groove 230A and the locking spring 230B to accept the wiper blade end-piece 228 and the notched baffle 236 ensure precise and correct installation.
In one preferred embodiment the web-cleaning device includes a baffle 202 that is positioned within the sump housing to prevent the sudden displacement and subsequent spillage of scavenged particular material when the bracket assembly is moved to the service position during which the web-cleaning device can be removed.
The web-cleaning cartridge 156 is attached to a lower bracket assembly 154 by the retracting the stems on the side plungers 168 and pressing the cartridge into the opening of the lower bracket until the stems align with the slots 166 on the sides of the cartridge, and then installed into backup shoe assembly 152 for selectively positioning said web-cleaning apparatus 150 in a web-cleaning position in which said web-cleaning apparatus pressingly engages the web surface. The lower bracket assembly 154 and the backup shoe assembly 152 selectively positions the web-cleaning apparatus in a web-cleaning position, as shown in
In a preferred embodiment, the end springs 188 can force contact of the four strategically placed stops 192 in the sump in tight contact with the shoe 170, allowing for higher precision of blade engagement with the transport web 128. This is accomplished as the end springs 188 rest on the lower bracket flat surfaces 184 and 186 and as the lower bracket is latched at front with the backup assembly, this action causes the spring to be compressed thus forcing the sump towards the shoe until the stops prevent any further motion. By controlling the depth of the blade groove with respect to the stops and the blade dimension from the end piece resting on the groove to the blade edge contacting the web, the amount of interference between the flexible blade material component 227 of the wiper blade with the shoe can be controlled.
In another embodiment of the web cleaning cartridge 156, the cleaner sump 198 has molded grooves 230A with screw inserts 230D that can be used with proper tool blades (not shown) in a setup fixture (not shown here) to set up each sump so as to fix blade engagement and to eliminate imprecision in the locating features of the molded sump that locate the cleaning blades. Once the screws are set, they can be permanently glued in place as to not move during the operating life of the sump and to prevent any tampering with the set up as previously described.
Another molded component of the sump housing includes a slot 166 that lockedly engages the stem ST of the plunger 168 on the sides of lower bracket assembly 154. In a preferred embodiment it is important that the sump housing 198, including all its features, be molded with a static dissipating material. This is critical to prevent the unwanted build-up of static charge that would interfere with quality and efficiency during the printing process and possibly damage equipment and make the operators experience unpleasant.
One preferred embodiment of the sump has a combination of the above features, including one or more stops 192, one or more side seals 222, a continuous gasket seal 234, the Mylar blade seal 224 adjacent each wiper blade 194A,B. It also would have the end springs 188 mounted to the body at front and at rear, and said springs resting on the top surface of the lower bracket and the bottom surface of the sump housing, to provide a normal force that is distributed between the above mentioned stops 192, when the lower bracket assembly is latched at front to the backup shoe assembly and supported at the rear by the pins, to bias the stops toward the back up shoe assembly. The web-cleaning cartridge would also have baffles 202 with one or more notches 236 that prevent misplacement of the wiper blades; one or more releasable wiper blade(s) including a releasable feature, each having spring 230B, to lock the wiper blade in the optimum location in the sump so that the blades do not fall out when inverted to dump waste materials; and a removable cover to facilitate the removal of debris material from the sump without removing the wiper blade(s).
The end pieces hold the two or more releasable wiper blade(s), each having a distinguishment wherein the one or more placement device(s) to cooperate with the distinguishment to hold one wiper blade in place proximate the other wiper blade. The distinguishment is shown in
For cleaning of oil absorbing and/or coated web that are generally significantly more abrasive than uncoated version of the transport web, we have found that the cleaning edge of Polyurethane blades can be tom apart quite rapidly and increasing the Polyurethane blade stiffness will accelerate the damage so that fine line streaks can develop on the web surface and in particular over the same regions where the web interacts with paper and these fine line streaks are so tightly attached to the web surface that it cannot be wiped with typical Polyurethane blade material. For the uncoated web applications, there are also a few peculiar substrates or papers that have components that will deposit on the web surface and stick to it so tightly that it cannot be removed by the typical Polyurethane blade materials and these deposits also tear the Polyurethane blade edges and render these blades ineffective for the cleaning operation. In the above applications, the blade material component must be harder and more wear resistance while at the same time has controllable wear instead of the tear found with Polyurethane. While it is possible to use much harder variations of Polyurethane, a desire to arrive at a blade and coated web transport that will have considerably longer operational life blade led to an investigation into using metallic material blade component 227. The wear resistance formulation of the coated transport web disclosed by W. Ferrar et al in disclosure # provided the right coating for enabling the application of metallic blades.
Placement of metallic materials as the blade material component 227 of wiper blade 194A in the upstream position has shown to be more effective when cleaning oil absorbing and/or coated webs that are significantly more abrasive and rougher than uncoated version of this web. The Rz, a roughness measurement describing the height from the peak to the valley of a surface and the abrasive characteristic of the web such as a Gamma-Aluminum coated belt with a particle size of 0.5 microns or less for the coated web is between 1-4 u versus typically less than 1 u for the uncoated type. The profiled metallic blade has been shown to be very effective to remove paper contamination that is stuck to the web surface and that is not effectively removed by typical blade materials such as Polyurethane blades. The upstream wiper blade is found to do most of the cleaning action. The above embodiment provides better cleaning perfomance when smaller toner particles are used or in an oiless or nearly oil less environment or when dealing with paper substrates that are more likely to leave a filming of paper contaminants that are tightly attached to the web transport. One skilled in the art understands that this could be achieved with one blade or cumulatively with a plurality of blades or blade segments.
The first metallic material tested successfully was a Phosphor bronze, such as UNC C51000 per ASTM B103, with an elastic modulus of 16 kpsi with a free extension, W, of 0.250″ and 0.005″ thickness, t, and attached to the blade stiffener by double sided tape and at an engagement of 0.015″. The blade angle with the web was close to 80 degrees in the undeflected state. The blade material component had been made of uniform thickness profile as shown in FIGS. 6 and 8A-B using photoetching process. The ends of the Phosphor Bronze blade were rounded to a radius of 2 mm to avoid a sharp corner. For the corners of the metal or metallic blade, it is recommended a radius of 1-5 mm. This blade was installed as the first blade and the second blade was that of a typical Polyurethane blade material of uniform thickness profile as shown in FIGS. 6 and 8A-B, with 0.050″ thick, 0.250″ or 0.050″ free extension and elastic modulus close to 1000 psi at close to 0.015″ engagement.
A typical cleaning blade of uniform thickness profile is shown where 227A may be either made of a metallic material or a polyurethane material, with a free extension W, total width of W′ and thickness t that is glued to a steel blade stiffener 228 having end-pieces 228a,b is shown in
In another example both a 0.0025″ and a 0.003″ (t) strip would break the uniform thickness profile, as shown in
Another embodiment of the profiled metal blade that was made and tested had ribbing as shown in
Another embodiment would have a metallic blade as the first blade 194A and a Polyurethane blade as the second blade 194B and a third embodiment would have two metallic blades so a small defect on the cleaning edge of one blade might not degrade cleaning performance as it is unlikely both blades would have a edge defect in the same location. If two blades are used, they could have the same stiffness/unit length or preferably a stiffer blade in the first position and a less stiff blade in the second position. Furthermore, the metallic blade component could be of uniform profile or thickness 227A or of a variable or stepped thickness profile 227B as shown in
Other clamping techniques and configurations of mounting for blade component 227A or 227B can be used to accomplish the same task as shown in
In a preferred embodiment the ends or corners of the metallic blade material component 227 are rounded to avoid a sharp corner and typically the radius should be 1-5 mm. Due to the thin nature of profiled metallic blade component and the edge sharpness as a required for functionality, warning labels WL are placed on the cover assembly and can also be added to each metallic blade assembly to warn the operator to carefully handle this blade and its edge. The metallic blade is also more susceptible to permanent deformation, kinks and damage so it must be handled with care.
Stiffness is measured by (E*L/4) (t/W)̂3, where E is the elastic modulus of the blade material, L, t, and W are the blade material component 227 length, thickness and free extension in contact with the web so thickness is one of a number of ways to achieve a stiffer blade, any of which could be used. The free extension W is usually the distance from the end of the blade that will contact the surface to be cleaned to the fixed end of the blade that is held by the blade holder. For stepped thickness blades or variable profile blades, an equivalent stiffness can be calculated based on the variable profile of the thickness and the free extension or the clamping conditions through Finite Element Analysis. Note that this simple beam calculation is for an evenly clamped support on both sides of the blade. If the constraint of the blade is clamped unevenly and depending on which side of the stepped beamed is facing the blade holding support bracket, it will affect the stiffness. In these cases the finite element analysis can be used to calculate the effective stiffness due to nonlinear clamping of its boundary conditions. Since metallic materials have considerably higher elastic modulus, they need to be considerably thinner than Polyurethane blades. For Polyurethane blades, the range of stiffness/unit length is selected in the range of 2-5 psi and for the preferred embodiment of the metallic blade; the stiffness/unit length can be from 2-32 psi, and best in the 2-16 psi. For one of the proposed embodiment, the uniform thickness profile can be in the range of 0.002-0.0035″ with a free extension of 0.200″-0.350″ and an engagement in the range of 0.010″ to 0.035″. The stiffness/unit length is selected to control the torque load imposed by the cleaner on the moving web and the load force or engagement needed to arrive at an acceptable and long lasting cleaning performance. Blade hardness will also play a factor in the torque load and blade wear and stiffness as the elastic modulus can be derived from it. The stiffener plate is selected with a lower leg bend to increase stiffness to reduce bowing and vibrations. With the introduction of stiffer blade, noise and vibration of the cleaner and web can ensue and that can lead to blade edge damage. To reduce the noise and vibrations, we can increase the stiffener thickness, add embossment to the flat portion across its length, elongate the lower leg, add a center support point and also change the thickness of the locking springs as discussed earlier. Some of these techniques are implemented in this cleaner but not shown here.
Due to the stiffer blade selection for the metallic or even if a higher stiffness Polyurethane blade is selected, the wiper blade 194A, B load onto the shoe assembly along with the loading from the stops 192 can be high enough to generate a bowing or deformation on the shoe away from the blade that can reach in some cases 0.005-0.010″ and this would reduce the effective blade engagement across the blade length and may lead to poor cleaning as the metallic blade wears. To resolve this problem, a preferred embodiment of the shoe 170 is that of an extrusion or machined part of high enough rigidity to reduce the above deformations to a level below 0.003″ and in this case a “I-shaped” extrusion is selected as shown in
In a preferred embodiment the Polyurethane material for the wiper blade can be made from polyester polyurethane with the following properties: a hardness of between 60 and 85 Shore A, an initial (or Young's) modulus of between 500 and 1500 psi, a Bayshore resiliency above 30%, and a compression set lower than 25% as is described in the aforementioned cross-referenced U.S. Pat. No. 6,453,134, issued on Sep. 17, 2002, in the names of Ziegelmuller et al., the contents of which being hereby incorporated by reference herein. The two cleaner blades could involve other distinguishments such as a first blade being a metallic blade which has higher stiffness than the second blade which is also a metallic blade and their respective blade holders are of different thickness so that the placement of the blades is easy for an operator to distinguish.
In one embodiment of the toner removal apparatus for cleaning particulate material from a moving surface in an electrographic printer that is adapted to contact the surface to remove particles from the surface has two or more releasable wiper blades. At least one of the releasable wiper blades is a profiled metal blade for example a first blade that is closest to a first cleaning contact point. A holder having one or more placement devices cooperates with the profiled metal blade to hold the blade in place proximate a surface at a working angle of 40-75 degrees for cleaning particulate material from a moving a surface. In one preferred embodiment the profiled metal blade has a stepped thickness profile. The stepped profile thickness can have an etched profile as discussed above. Specifically the etched profile could range between 0.002″ to 0.003″ on the contact edge, 0.005″ on a held edge, with a free extension for the etched profile of 0.250″ and the stepped down thickness ranging from an extension of 0.180″ to 0.325″ from the contact edge. The image on the right could also be made by etched from both sides therefore be tapered or ragged on both front and back and scaling to work via the desired contact force. In another embodiment for wear rates up to 6000,000 papers an engagement of 0.015 to 0.035. Note that the beam length is the free extension and not the L in K/L where L is the length of the blade needed to clean across the web.
The stepped profile can have a width narrower than the blade free extension for varying the stiffness/length ratio for the blade. The varying stiffness can be designed to effectively clean a movable web surface, coated or uncoated, having a Rz, roughness between less then 1 to 4 microns as well as a coated Gamma-Aluminum web having abrasive particles size of 0.5 microns or less. The profiled metal blades can have one or more rounded corners with a radius of 1-5 mm to enhance cleaning without damaging the web. The apparatus can have two or more blade holders so that the holders enable a free extension of 0.200″-0.350″ and an engagement in the range of 0.010″ to 0.035″. The stepped thickness profile can be held at the thickest portion of the blade so that a thinner thickness profile extends beyond the free extension to reduce the blade stiffness and/or a thinner thickness profile shorter than the free extension to increase the blade stiffness. The blades can be one or more metal blades and/or one or more polyurethane blades having a stiffness/unit length from 2-5 psi and one or more metallic blades having a stiffness/unit length from 2-16 psi. and an uniform thickness profile between 0.002-0.0035″. For example the two cleaner blades could include a first metallic blade closest to a first cleaning contact having a higher stiffness than a second metallic blade, such as a stiffness/unit length, K/L of 2-32 psi. The second blade could alternatively have the same stiffness and/or a lower stiffness. In another embodiment, there might be only one metallic blade which seats in the second position and has the required properties to maintain good cleaning performance.
In other embodiments the first blade has a longer length discussed above can act as a distinguishment and locator since the longer blade would not fit in the shorter position. Other changes, such as matching keys, can be used to prevent mis-location of the blades. Note that either the metallic or the polyurethane components can be attached to the blade stiffener through permanent glue and for either edge can be used as the cleaning edge.
When a first blade is stiffer it allows the removable of tough materials from the web than the second blade less stiff blade. For the metallic component blade either of uniform thickness 227A or profiled thickness 227B, the stiffness/unit length, K/L, has been found to be best in the range of 2-16 psi, but it can go up to 32 psi. In the profiled metallic blade, the material can be photoetched to generate a desirable profile as shown in
Other manufacturing methods for fabricating the Metallic blades are possible including shearing, grinding and polishing to generate square edges or electropolishing to round the edges. One such method of shearing a metallic shims and producing what is called in the trade as “edge number 3” than can produce a rounded and a sharp edge of good enough quality for such blade cleaning applications. The edge should have a radius of less than 10 u, preferably less than 5 u, but given the more controlled wear of a Metallic blade against the coated transport web, the edge radius should become sharper with use. The sheared edge #3 edge quality was tested for IC/BC conductive brushes and successfully cleaned metallic detone rollers for 750-2.2M prints. A metallic blade edge can be fabricated by shearing to produce an edge quality referred to in the trade as Number 3, and produce one of a round edge, a square edge or either edge can be used as the cleaning contact with the web.
One skilled in the all will understand that this apparatus can allow the lower portion of the sump body to engage the lower bracket assembly in such a way that the assembly prevents the operator from removing the sump assembly incorrectly, thus causing damage to the end springs and other components, or inserting the sump assembly incorrectly. The sump can be removed by pulling out the stems on the plungers on the sides of the lower bracket. In one preferred embodiment this'safeguard requires the operator to remove the lower bracket assembly with the sump assembly as a unit for servicing such as dumping waste, replacing customer replaceable wiper blades or cover assembly, or vacuum cleaning the cover especially around the end seals.
The lower bracket assembly is pivotally mounted to one end of the back-up shoe assembly to enable the cleaning apparatus to be moved between an operative position (shown in
The cleaning apparatus allows a method for assisting a customer in removing a web-cleaning apparatus adapted to contact a surface of a moving web and to remove particles from the web with a quick release device to be greatly simplified. The customer will first release the latch at the front of the lower bracket from its latching keeper at the front bracket of the backup assembly and then remove the lower bracket assembly with the web-cleaning apparatus. The latter can then be placed on a table for further servicing. For servicing the web cleaning apparatus, the customer will remove a releasable cover component by first loosening the fasteners on the cover and then rotating the cover out of the upper boss in the sump and about the hinge/slot features of the cover and sump and then pulling the binges out of the slots. This enables the cover to be physically de-coupled from the sump and/or lower bracket to facilitate the removal of debris material from the sump without removing the wiper blade(s). The operator might prefer to remove the web cleaning apparatus from the lower bracket and this can be done by pulling the plunger out to retract the stem on the side of the lower bracket to disengage the stems from the slot features on the sides of the web-cleaning cartridge and this operation which enables the lower bracket assembly to be physically de-coupled from the sump thereby facilitating assembly or web service and/or replacement. Then a releasable wiper blade component including an end piece and distinguishment that locks the wiper blade in the optimum location in the sump so that the blades do not fall out when inverted but is releasable from the sump and cover to facilitate the removal of debris material from the sump after removal of the wiper blade(s) or for replacing the customer replaceable wiper blades. While the wiper blades are releasable from the cleaner, the thin nature and sharpness of the metallic blade requires special attention by the operator and a warning label WL is placed on the cover of the cleaner sump and each metallic blade to avoid any cuts or scrapes with the blade edge.
If the customer is using a preferred embodiment discussed above, the customer will only have to remove the lower bracket assembly with the web cleaning apparatus as a unit. This avoids damage to the end springs by too much handling of the apparatus from the operator and provides the customer a number of additional safety features. These safety features are based on the fact that if the web cleaning apparatus were easily replaceable then when the operator were to install the spring loaded cleaner, the springs at rear could interfere with the lower bracket feature at the rear and this might lead to damage to the spring, or sump feature that allows the attachment of the spring to the sump.
The customer should be able to remove the cover assembly and then invert the lower bracket with the sump assembly in place to dump the waste material into an anti-static plastic bag or a similarly suited container without having to remove the wiper blades. The customer might prefer to dump the waste by removing the wiper blades to vacuum clean the sump or by other means. Because of the inherent higher precision of mounting the wiper blades to the web surface the web cleaning apparatus reduces the variability in the torque load against the web drive plus it also allows for lower wiper blade engagement with the web and thus reducing the torque load needed for cleaning said web of particulates. Lower wiper blade engagement allows for higher blade working angle with the moving web, which is more effective to cleaning operation. The de-coupling of the sump from the lower bracket assembly might only be required if a new web cleaning apparatus is needed. We expect this operation to seldom be needed.
The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.
